1. Field of the Invention
The present invention relates to a gas generator for an air bag used in air bag systems for vehicles.
2. Description of the Related Art
In gas generators in which gas generating agents having a solid form (shaped as tablets, cylinders, etc.) are used, ignition energy (a high-temperature gas, a flame, etc.) generated by the activation of an igniter causes a gas generating agent to ignite and burn; or alternatively, a transfer charge is ignited by an igniter, and the released ignition energy causes a gas generating agent to ignite and burn.
In the gas generator, a large shockwave is created upon generation of the ignition energy due to the activation of the igniter; if this shockwave hits the gas generating agent directly, the gas generating agent may break as a result. The fragmentation of the gas generating agent results in an increased surface area of the same, which increases also the amount of gas generated during initial combustion, making thereby impossible to maintain combustibility as originally designed.
U.S. Pat. No. 5,345,875 discloses a gas generator in which a combustion chamber is divided into two by a shockwave barrier 60, one of the combustion chambers (first combustion chamber) faces the activation portion of an igniter 24, and the other combustion chamber (second combustion chamber) communicates with the first combustion chamber through a plurality of communication holes 64 formed in the barrier 60.
In U.S. Pat. No. 5,345,875, the igniter 24 and the two combustion chambers are arranged in series, so that the ignition energy advances directly into the first combustion chamber, and also into the second combustion chamber via the communication holes 64, which might result in a fragmentation of the gas generating agent by the shockwave.
In the constitution of conventional gas generators, the ignition energy generated by the activation of the igniter, in the form of a shockwave, collides directly with the gas generating agent, which may cause the fragmentation of the solid gas generating agent, increasing the surface area thereof and making thereby impossible to maintain combustibility as originally designed.